Welding power supply with adjustable resistance

Abstract

A welding system includes a consumable welding electrode, a feeder that advances the consumable welding electrode toward a weld puddle during a welding operation, and a power supply configured to provide a series of welding waveforms to the consumable welding electrode to generate a welding current in the consumable welding electrode. An individual welding waveform of said series includes a predetermined minimum current portion, a peak current portion, and a background current portion having a magnitude that is greater than the minimum current portion and less than the peak current portion. The power supply comprises an adjustable resistance for setting a magnitude of the minimum current portion. The adjustable resistance is connected in series with the consumable welding electrode such that the minimum current portion of the welding current flows through the adjustable resistance.

What is claimed is: 
     
         1 . A welding system, comprising:
 a consumable welding electrode;   a feeder that advances the consumable welding electrode toward a weld puddle during a welding operation; and   a power supply configured to provide a series of welding waveforms to the consumable welding electrode to generate a welding current in the consumable welding electrode, wherein an individual welding waveform of said series includes:
 a predetermined minimum current portion; 
 a peak current portion; and 
 a background current portion having a magnitude that is greater than the minimum current portion and less than the peak current portion, 
   wherein the power supply comprises an adjustable resistance for setting a magnitude of the minimum current portion, and the adjustable resistance is connected in series with the consumable welding electrode such that the minimum current portion of the welding current flows through the adjustable resistance.   
     
     
         2 . The welding system of  claim 1 , further comprising an output switch connected in parallel with the adjustable resistance, wherein the peak current portion and the background current portion of the welding current flow through the output switch and the consumable welding electrode. 
     
     
         3 . The welding system of  claim 1 , wherein the adjustable resistance comprises a plurality of individually switched resistances connected in parallel. 
     
     
         4 . The welding system of  claim 3 , wherein the individually switched resistances have respective different resistance values. 
     
     
         5 . The welding system of  claim 3 , wherein the individually switched resistances have resistance values less than 20 Ohms. 
     
     
         6 . The welding system of  claim 1 , wherein the power supply is configured to automatically adjust a resistance level of the adjustable resistance based on a wire feed speed at which the feeder advances the consumable welding electrode. 
     
     
         7 . The welding system of  claim 1 , wherein:
 the adjustable resistance comprises a series connection of a first transistor and a first resistor, and a series connection of a second transistor and a second resistor,   the series connection of the first transistor and the first resistor is connected in parallel with the series connection of the second transistor and the second resistor, and   the first resistor has a different resistance value than the second resistor.   
     
     
         8 . The welding system of  claim 7 , further comprising an output transistor connected in parallel with the adjustable resistance. 
     
     
         9 . A welding system, comprising:
 a consumable welding electrode;   a feeder that advances the consumable welding electrode toward a weld puddle during a welding operation; and   a power supply configured to provide a series of welding waveforms to the consumable welding electrode to generate a welding current in the consumable welding electrode, wherein an individual welding waveform of said series includes:
 a predetermined minimum current portion; 
 a peak current portion; and 
 a background current portion having a magnitude that is greater than the minimum current portion and less than the peak current portion, 
   wherein the power supply comprises:
 an output switch; 
 an adjustable resistance connected in parallel with the output switch; and 
 a controller operatively connected to both of the output switch and the adjustable resistance, and configured to control switching operations of the output switch between an on state and an off state, and to control a resistance level of the adjustable resistance, 
   wherein the output switch is in the on state during the peak current portion and the background portion of the welding current, such that the peak current portion and the background current portion flow through the output switch and through the consumable welding electrode, and the output switch is in the off state during the minimum current portion of the welding waveform such that the minimum current portion flows through adjustable resistance and through the consumable welding electrode.   
     
     
         10 . The welding system of  claim 9 , wherein the adjustable resistance comprises a plurality of individually switched resistances connected in parallel. 
     
     
         11 . The welding system of  claim 10 , wherein the individually switched resistances have respective different resistance values. 
     
     
         12 . The welding system of  claim 10 , wherein the individually switched resistances have resistance values less than 20 Ohms. 
     
     
         13 . The welding system of  claim 9 , wherein the controller is configured to automatically adjust a resistance level of the adjustable resistance based on a wire feed speed of said feeder. 
     
     
         14 . The welding system of  claim 9 , further comprising a second output switch and a second adjustable resistance connected in parallel with the second output switch, wherein the power supply is configured to provide AC welding waveforms to the consumable welding electrode. 
     
     
         15 . The welding system of  claim 9 , wherein:
 the adjustable resistance comprises a series connection of a first transistor and a first resistor, a series connection of a second transistor and a second resistor, and a series connection of a third transistor and a third resistor, and   the series connection of the first transistor and the first resistor is connected in parallel with the series connection of the second transistor and the second resistor, and is further connected in parallel with the series connection of the third transistor and the third resistor.   
     
     
         16 . A welding system, comprising:
 a welding electrode;   a power supply configured to provide a series of welding waveforms to the welding electrode to generate a welding current in the welding electrode, wherein an individual welding waveform of said series includes:
 a predetermined minimum current portion; 
 a peak current portion; and 
 a background current portion having a magnitude that is greater than the minimum current portion and less than the peak current portion, 
   wherein the power supply comprises:
 an output switch; 
 an adjustable resistance comprising an array of individually switched resistances connected in parallel with the output switch; and 
 a controller operatively connected to the output switch and to the array of individually switched resistances, and configured to control switching operations of the output switch, and to control a resistance level of the adjustable resistance by controlling activation of the individually switched resistances, 
   wherein the controller controls the switching operations of the output switch and the activation of the individually switched resistances such that the peak current portion and the background current portion of the welding current flow through the output switch and the welding electrode, and the minimum current portion of the welding waveform flows through the adjustable resistance and the welding electrode.   
     
     
         17 . The welding system of  claim 16 , wherein the individually switched resistances have respective different resistance values. 
     
     
         18 . The welding system of  claim 16 , wherein the individually switched resistances have resistance values less than 20 Ohms. 
     
     
         19 . The welding system of  claim 16 , further comprising a wire feeder that feeds the welding electrode at a wire feed speed, wherein the controller is configured to automatically adjust a resistance level of the adjustable resistance based on the wire feed speed. 
     
     
         20 . The welding system of  claim 16 , wherein:
 the array of individually switched resistances comprises a series connection of a first transistor and a first resistor, a series connection of a second transistor and a second resistor, and a series connection of a third transistor and a third resistor, and   the series connection of the first transistor and the first resistor is connected in parallel with the series connection of the second transistor and the second resistor, and is further connected in parallel with the series connection of the third transistor and the third resistor.